Network operators or communication service providers use administrative costing to determine network paths to communicate across a data network. An administrative cost (i.e., a cost) is an indication or a measure of the performance associated with transmitting data via a particular network segment or network path. For example, a network operator may determine a cost associated with a plurality of network paths between a source node and a destination node and select the network path associated with the least administrative cost to communicate the data. In traditional communication systems a cost for a network path is determined based on network congestion delay, bandwidth availability, and/or the number of switch hops associated with that network path.
Traditional routing methods for frame relay (FR) and asynchronous transfer mode (ATM) networks typically use routing protocols such as a Private Network to Network Interface (PNNI) protocol to exchange routing information between switches and Open Shortest Path First (OSPF) algorithms to determine network paths. In traditional systems, the routing information includes costs based on network congestion delay, available bandwidth, switch hops, etc. between source and destination switches. Each switch in a network uses the routing information and OSPF to determine a shortest path between that switch and a destination switch based on network congestion delay, available bandwidth, or a number of switch hops and attempts to communicate data via the shortest path, which is associated with the lowest cost.
Traditional methods that use network delay, bandwidth, or switch hops as the cost measure for selecting a network path are often not suitable for determining a network path across a network spanning a relatively large geographical distance or area (e.g., a nationwide network or an international network). For example, the network congestion delay or available bandwidth at any particular switch in a nationwide network may be miniscule compared to the geographical or physical distance through which data must be communicated. When such is the case, selecting a network path based on the least congestion delay may not provide the network path associated with the least data transmission time.
Further, traditional network systems typically use PNNI or Hierarchical PNNI (HPNNI) routing protocols throughout an entire network to determine network paths. The PNNI routing protocol requires each switch in a network to obtain routing information associated with the entire topology of the network or routing information required to communicate with every switch in the network. The HPNNI routing protocol is implemented by dividing an entire network into peer groups. In this case, each switch within a peer group obtains detailed routing information associated with communicating with switches in the same peer group. To communicate with switches in other peer groups each switch in a peer group obtains via switches designated as peer group leaders only general routing information associated with communicating with switches in other peer groups.
The PNNI and HPNNI routing protocols require switches to advertise routing information to other switches. In this manner, when switches establish a network path the switches can use the routing information to establish the network path. Each time a switch advertises its routing information, the switch must build a routing table by gathering routing information associated with its routing perception of the network or at least of the switches to which it directly communicates. The switch must then transmit the routing information from the routing table to the requesting switch. As more nodes or switches are added to a network and the network becomes larger, advertising costs in this manner becomes relatively more demanding on each switch. For example, gathering the routing information requires more and more processing power and time as a network grows. Also, the amount of memory required to store the routing information becomes relatively large. Typically, the processing power and memory requirements restrict the PNNI routing protocol to be used in limited-sized networks because of the manner in which the PNNI routing protocol requires each switch to obtain routing information about the entire topology of the network. Some traditional methods use HPNNI to overcome the scalability limitations associated with PNNI. However, these traditional methods typically produce sub-optimal end-to-end routing decisions.